Intravascular deliverable stent for reinforcement of abdominal aortic aneurysm

Abstract

A stent/graft especially designed to be used in a minimally invasive surgical procedure for treating an abdominal aortic aneurysm (AAA) comprises an innermost tubular structure of a length (L 1 ) formed by braiding a relatively few strands of shape memory alloy wire. The pick and pitch of the braid are such as to provide relative large fenestrations in the tubular wall. A portion of the innermost tubular structure of a length L 2 <L 1 is surrounded by a further braided tubular structure having relatively many strands that occlude the fenestrations of the innermost tubular structure. The composite structure can be stretched to reduce the outer diameter of the stent/graft, allowing it to be drawn into a lumen of a delivery catheter. The catheter can then be advanced through the vascular system to the site of the AAA and then ejected, allowing it to self-expand with the portion L 2 bridging the aneurysm. The portion L 1 >L 2 does not block blood flow to the renal arteries while the portion L 2 prevents the aneurysm to grown and burst.

What is claimed is: 
     
       1. A catheter deliverable stent for treating an abdominal aortic aneurysm comprising:
 a continuous innermost tubular structure having a first length and comprising a first plurality of braided strands forming a first braid comprising a first shape memory alloy, the first braid of the continuous innermost tubular structure having a predetermined pick and pitch to define openings sufficiently large so as to not materially impede blood flow therethrough, the first braid extending from a first end of the innermost tubular structure to a second end of the innermost tubular structure; 
 a continuous outer tubular structure having a second length less than the first length and comprising a second plurality of braided strands forming a second braid comprising a second shape memory alloy, the second braid of the continuous outer tubular structure having a predetermined pick and pitch to define openings sufficiently small so as to substantially preclude blood flow therethrough, the continuous outer tubular structure being in a coaxial relationship with and surrounding the continuous innermost tubular structure, wherein the continuous innermost tubular structure and the continuous outer tubular structure are both adapted to self expand and together form a composite tubular structure having a predetermined diameter; 
 wherein a longitudinal stretching of the composite tubular structure reduces the outer diameter of the composite tubular structure sufficiently to allow the composite tubular structure to be loaded into a lumen of an intravascular delivery catheter, and wherein release of the composite tubular structure from the intravascular delivery catheter allows the composite tubular structure to self expand back to said predetermined diameter. 
 
     
     
       2. The catheter deliverable stent according to  claim 1 , wherein a portion of the continuous innermost tubular structure extending beyond a terminus of the continuous outer tubular structure is adapted to overlay the juncture of a patient's renal arteries within the patient's abdominal aorta when the continuous outer tubular structure bridges an abdominal aortic aneurysm. 
     
     
       3. The catheter deliverable stent according to  claim 1 , further comprising an additional outermost tubular structure placed in a generally coaxial surrounding relationship with the continuous outer tubular structure along at least a length portion thereof. 
     
     
       4. The catheter deliverable stent according to  claim 3 , wherein the additional outermost tubular structure and the continuous outer tubular structure each respectively comprise 144 braided wire strands. 
     
     
       5. The catheter deliverable stent according to  claim 3 , wherein the outermost tubular structure comprises a third plurality of braided strands forming a third braid, the third braid having a predetermined pick and pitch to define openings sufficiently small so as to substantially preclude blood flow therethrough. 
     
     
       6. The catheter deliverable stent according to  claim 5 , wherein the second braid and the third braid define openings equal in area. 
     
     
       7. The catheter deliverable stent according to  claim 1 , wherein the first braid comprising said plurality of braided strands comprises 36 wire strands and the second braid comprising said plurality of braided strands comprises 144 wire strands. 
     
     
       8. The catheter deliverable stent according to  claim 1 , wherein the continuous innermost tubular structure is flared outward. 
     
     
       9. The catheter deliverable stent according to  claim 1 , wherein the first braid defines openings having an area of about 0.0016 square inches and the second braid defines openings having an area of about 0.0001 square inches. 
     
     
       10. The catheter deliverable stent according to  claim 1 , wherein the continuous innermost tubular structure comprises wires having a diameter of from 0.002-0.010 inch and the continuous outer tubular structure comprises wires having a diameter of about 0.001 inch. 
     
     
       11. The catheter deliverable stent according to  claim 1 , wherein the first shape memory alloy is the same as the second shape memory alloy. 
     
     
       12. A catheter deliverable stent for treating an abdominal aortic aneurysm comprising:
 an innermost tubular structure having a first length, first and second ends and comprised of a first plurality of braided strands of a shape memory alloy, wherein the innermost tubular structure has a predetermined pick and pitch extending from the first to the second end and defining openings across the entire first length having an area sufficiently large so as to not materially impede blood flow therethrough; 
 an outer tubular structure having a second length shorter than the first length, first and second ends, and comprised of a second plurality of braided strands of a shape memory alloy, wherein the outer tubular structure has a predetermined pick and pitch to define openings having an area sufficiently small so as to substantially preclude blood flow therethrough; 
 the innermost tubular structure and the outer tubular structure each having a preset expanded diameter and being self expandable from a compressed diameter to the preset expanded diameter, the innermost tubular structure surrounded by and coaxial with the outer tubular structure to form a composite tubular structure; and 
 wherein a longitudinal stretching of the composite tubular structure reduces the outer diameter of the composite tubular structure sufficiently to allow the structure to be loaded into a lumen of an intravascular delivery catheter, and wherein release of the composite tubular structure from the catheter allows the structure to self expand back to said predetermined diameter.